Evaporation and condensation dynamics within saturated epiphyte communities in a Quercus virginiana forest (coastal Georgia, USA)

Abstract

Rainfall-forest interactions significantly impacts hydrological, ecological, and societal systems by altering rainwater supply to the surface. Canopy surfaces’ retention, evaporation, and redistribution of rain affect all storm-related hydrological processes. Arboreal epiphytes, plants that live on forest canopies, can store and evaporate substantial amounts of water, but their role in rainfall partitioning is under-researched compared to bark and leaves. Maritime forests of the southeastern U.S. have abundant epiphyte comunities, largely dominated by the resurrection fern (Pleopeltis polypodiodes), the bromeliad Spanish moss (Tillandsia usneoides), and foliose lichens. We assessed saturation time, evaporation during rain-saturated conditions, and condensation input within existing epiphyte vegetation on Quercus virginiana (southern live oak), a dominant host tree species, in the maritime forests on Skidaway Island (Savannah, GA, USA). Epiphyte assemblages were saturated for a median 35 % of the 3-month study. Wet canopy evaporation ranged from 0.06 to 0.42 mm h⁻¹, while wet canopy condensation was slightly lower, ranging from 0.01 to 0.15 mm h⁻¹. High total evaporation is likely dependent on the ability of epiphyte vegetation to remain saturated for long periods of time. Results from this study provide a basis for detailed ecohydrological research in epiphyte communities.